Is a format of audio/video data, which is the most popular today. It can contain files encoded by different codecs, but they will be played in sync and create a unified image to the end user. AVI container supports function in multi-threaded mode, and allows different ratios of audio and video codecs.
An SPX file is a Speex audio file saved within an Ogg Vorbis container. Speex is an open source patent-free audio format designed for speech compression. It supports variable bitrate (VBR) encoding and several features not found in other audio codecs. Some examples include embedded encoding, intensity stereo encoding, and voice activity detection.